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stb_sprintf: fix overflow in negating INT_MIN #1725

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hjbreg wants to merge 1 commit into nothings:master from hjbreg:master

hjbreg commented Dec 6, 2024

stbsp_sprintf failed for INT_MIN with %d. I found that there is a negative operation on signed integer may lead to overflow.

According to C11.6.2.6.9, I fixed this bug by negating unsigned integer.

#include <assert.h>
#include <limits.h>

#define STB_SPRINTF_IMPLEMENTATION
#include "stb_sprintf.h"

int main()
{
    int n = 0;
    char buf[64];
    n = stbsp_sprintf(buf, "%d", INT_MIN + 1);
    assert(n == 11);
    n = stbsp_sprintf(buf, "%d", INT_MIN);
    assert(n == 11);
    return 0;
}

gcc -std=c11 -O2 a.c && ./a.out

a.out: a.c:14: main: Assertion `n == 11' failed.
Aborted (core dumped)


          stb_sprintf: fix overflow in negating INT_MIN

3f11f0d

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